Tissue oximeter intraoperative system

ABSTRACT

An oximeter probe includes sensor head with a probe face having one or more sensor structures to make measurements, a handle, and an elastic member connected between the handle and the base. A user can hold the handle while measurements are made and the elastic member permits the handle to flex relative to the sensor head with one or more sensor structures.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 15/650,718, filed Jul. 14, 2017, issued as U.S. Pat. No.10,165,970 on Jan. 1, 2019, which is a continuation of U.S. patentapplication Ser. No. 15/168,836, filed May 31, 2016, issued as U.S. Pat.No. 9,706,954 on Jul. 18, 2017, which is a continuation of U.S. patentapplication Ser. No. 14/746,736, filed Jun. 22, 2015, issued as U.S.Pat. No. 9,351,686 on May 31, 2016, which is a continuation of U.S.patent application Ser. No. 14/017,021, filed Sep. 3, 2013, issued asU.S. Pat. No. 9,060,720 on Jun. 23, 2015, which is a continuation ofU.S. patent application Ser. No. 13/653,257, filed Oct. 16, 2012, issuedas U.S. Pat. No. 8,527,022 on Sep. 3, 2013, which is a continuation ofU.S. patent application Ser. No. 12/623,945, filed Nov. 23, 2009, issuedas U.S. Pat. No. 8,290,558 on Oct. 16, 2012. These applications areincorporated by reference along with all other references cited in thisapplication.

BACKGROUND OF THE INVENTION

This invention relates to the field of medical devices, and morespecifically to an oximeter tool with a pressure limiting mechanism.

Medical devices play a critical role in medicine. Users, such asdoctors, use medical devices to save lives and improve the well-beingand quality of life for patients. Numerous advancements in medicaldevices have been made over the last several decades. Some examplesinclude the operating microscope which allows surgeons to see andoperate on small tissue parts and the endoscope which allows forminimally invasive exams and procedures.

Other examples of medical devices include sensors which monitorpatients. Such sensors make measurements such as oxygen saturation oftissue, pulse, blood pressure, temperature, and other physiologicalmeasurements.

In some cases, these sensors are placed on or near the tissue to bemeasured, such as by using an adhesive to secure the sensor to thetissue. In other cases, it may not be possible or it may be difficult touse an adhesive. In these cases, the user may manually hold the sensoragainst the tissue. It can be difficult for the user to maintain aproper pressure or a range of proper pressures of the sensor against thetissue so that the sensor can make accurate measurements. For example,over the course of the monitoring the user may become tired or fatigued.This may lead the user to press the sensor against the tissue using anexcessive level of force. This can lead to undesirable changes in thetissue such as a disruption of the local perfusion which in turn maylead to inaccurate measurements.

Therefore, there is a need for a new and improved oximeter tool with apressure limiting mechanism.

BRIEF SUMMARY OF THE INVENTION

An oximeter probe includes sensor head with a probe face having one ormore sensor structures to make measurements, a handle, and an elasticmember connected between the handle and the base. A user can hold thehandle while measurements are made and the elastic member permits thehandle to flex relative to the sensor head with one or more sensorstructures.

In a specific implementation, an oximeter device includes a base portionto face a tissue to be measured, at least one sensor opening formed on abottom surface of the base portion, a handle, a spring, connectedbetween the base portion and the handle, a pair of limit stops includingan upper limit stop and a lower limit stop, and a stop pin. The stop pinis received between the upper and lower limit stops. The pair of limitstops is fixed relative to one of the handle or base portion. The stoppin is fixed relative to another of the handle or base portion. Thespring urges the upper limit stop and the stop pin apart to create afirst gap between the upper limit stop and the stop pin. The lower limitstop may contact the stop pin to limit a travel of the handle such aspreventing the handle from springing backwards.

In an implementation, the spring is connected at a first end of thehandle and a portion of the handle extending from the first end to asecond end of the handle, opposite the first end, extends withoutprojecting over the at least one sensor opening.

A height of the base portion between the bottom surface and a topsurface of the base portion, opposite the bottom surface, may be about 6millimeters or less. The spring may include plastic.

In a specific implementation, the pair of limit stops is closer to theat least one sensor opening than the spring. In another implementation,the spring is closer to the at least one sensor opening than the pair oflimit stops.

In a specific implementation, the upper limit stop and the stop pintouch to close the first gap when a force applied to the handle exceedsa threshold value. The pair of limit stops may be contained within arecess of the handle. In this implementation, the upper limit stop is ata first end of the recess. The lower limit stop is at a second end ofthe recess, opposite the first end.

In a specific implementation, the at least one sensor opening iscontained within a sensor unit. In this specific implementation, thesensor unit includes a first source structure, a second sourcestructure, a first detector structure including optical fiber, and asecond detector structure including optical fiber. A first distance isbetween the first source structure and the first detector structure. Asecond distance is between the first source structure and the seconddetector structure. A third distance is between the second sourcestructure and the first detector structure. A fourth distance is betweenthe second source structure and the second detector structure.

The first distance is not equal to the second, third, and fourthdistances. The second distance is not equal to the third and fourthdistances. The third distance is not equal to the fourth distance.

A first end of the handle may be supported by the spring and a secondend of the handle, opposite the first end, may be unsupported so thatthere is a second gap below the second end of the handle.

In a specific implementation, a method of making an oximeter deviceincludes providing a single piece of material including a base portion,a spring portion, and a handle portion. Attaching an oximeter sensor toa bottom surface of the base portion. Routing a cable of the oximetersensor through a channel in the handle portion. And attaching a pad tothe bottom surface of the base portion.

In another implementation, a method of making the device includesmolding the plastic handle, inserting the sensor head and cable throughthe handle, gluing the back of the sensor head to the handle, applyingan adhesive foam pad (e.g., one side of the foam pad is pre-coated withan adhesive and the other side of the foam is pre-covered with an opaqueadhesive light-shield film) such that the foam pad surrounds the sensorhead and sticks to the handle.

The method may further include forming a set of alternating ridges andvalleys on the handle portion. A thickness of a ridge may be equal to athickness of a valley. The ridges and valleys can help to improve grip,lighten the weight, or both. The ridges and valleys can help to reducemanufacturing costs. The single piece of material may include plastic(e.g., polypropylene, polyethylene, or polyurethane).

The pad may include foam. The pad may be referred to as a light shieldpad. In a specific implementation, the pad is compressible. One may seethe pad starts to be partially compressed when the force is in the orderof about 0.1 pounds or less (i.e., 45 grams or less). In this specificimplementation, the sensor head is not compressible and is equal to orgreater than the thickness of the foam pad which surrounds or at leastpartially surrounds the sensor head in a semi-annular horseshoe.Therefore, most of the applied force will be transmitted from thehandle, through the spring, to the incompressible sensor head, and theninto the contacting tissue.

In a specific implementation, the method further includes bending thespring portion and bringing the base and handle portion together toengage a stop pin of the base portion with a stop pin receiving regionof the handle portion.

In a specific implementation, an oximeter device includes a base portionto face a tissue to be measured, at least one sensor structure on abottom surface of the base portion, and a set of markings on a topsurface of the base portion, opposite the bottom surface, to aid inaligning the at least one sensor structure on the tissue. There is aspring and a handle connected to the base portion through the spring.The spring permits the handle to flex relative to the at least onesensor structure on the bottom surface of the base portion.

The spring may be a living hinge and the base portion, handle, andliving hinge may be molded as a single unit. A cross section of theliving hinge may include a middle region between opposite end regionsand a thickness of the living hinge may taper from the middle regiontowards the opposite end regions.

In a specific implementation, the set of markings includes a first arrowpointing towards a first side edge of the base portion, a second arrowpointing towards a second side edge of the base portion, opposite thefirst side edge, and a third arrow pointing towards a top edge of thebase portion, between the first and second side edges.

In a specific implementation, the oximeter device further includes anextension to offset the handle from the base portion. A first end of theextension is connected to the base portion. A second end of theextension, opposite the first end, is connected to the spring. A bottomsurface of the handle extends from the second end towards the first endand terminates before extending over the at least one sensor structure.

This tool or handle with an oximeter sensor head can be used duringreconstructive microsurgical procedures where there is a need to be ableto measure one or more regions of a flap intraoperatively. Some otherapplications include the real-time selection of perforator vessels bymeans of sequential clamping, mastectomy margin mapping, andconfirmation of flap reperfusion prior to leaving the operating room tohelp reduce take-back rates.

Existing designs using adhesive pads are not ideally suited forintraoperative use due to exposure of the adhesive pad to blood andfluids in the intraoperative sterile field which can reduce the padsadhesion when later applied. In addition, the variation in appliedpressure (which can alter the actual StO2 in a region of tissue) whenholding the sensor head to the flap by hand is generally considerablygreater than when the sensor head is adhesively applied, and thus amechanism to reduce pressure variation is desirable when spot-checksensing. Therefore an optimized small patch sensor fixation system forintraoperative use is needed.

The tool may be used to noninvasively estimate the percent oxygensaturation (StO2) in a volume of tissue. This may be performed inmedical environments including physician offices, hospitals, ambulatorycare, and emergency medical services. The tool may be indicated for usein monitoring patients during circulatory or perfusion examinations ofskeletal muscle or when there is a suspicion of compromised circulation.

In a specific implementation, a small patch sensor for use on flaps isintegrated into a permanently affixed pressure control handpiece withlight shield. The intraop sensor is provided as a sterile disposable.The tool is resistant to moisture. The sensor cable is routed throughthe tool to allow for cable strain resistance.

The tool may be used in the operating room environment, where strongoperating room lighting is expected. In addition, it should be notedthat the sensor and oximeter meets EMC emission requirements forpreventing interference with standard operating room equipment. The toolis easy to use, and the sensor can be reliably positioned onto the flapwith controlled pressure for stable StO2 readings. The tool is usable inoperating room lighting conditions.

Typically, fully biocompatible medical-grade materials are used for thepatient contacting portion of the sensor (or intraop sensor). Inaddition, electrical and laser hazard risks are mitigated in accordancewith IEC-60601-1 (Medical Electrical Safety) and IEC60825-1 (LaserSafety) standards.

Other objects, features, and advantages of the present invention willbecome apparent upon consideration of the following detailed descriptionand the accompanying drawings, in which like reference designationsrepresent like features throughout the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram for measuring oxygen saturation of tissuein a patient.

FIG. 2 shows in greater detail a specific implementation of the systemof FIG. 1.

FIG. 3A shows a block diagram of a tool having a sensor, pressurecontrol mechanism, and handle.

FIG. 3B shows a schematic diagram of a specific implementation of thetool.

FIG. 4 shows a side view of a specific implementation of the tool ofFIG. 3B.

FIG. 5 shows a perspective view of the tool.

FIG. 6 shows a side view of the tool.

FIG. 7 shows a section view of the tool.

FIG. 8 shows an enlarged view of the section view shown in FIG. 7.

FIG. 9 shows a front view of the tool.

FIG. 10 shows a rear view of the tool.

FIG. 11 shows a top view of the tool.

FIG. 12 shows a bottom view of the tool.

FIG. 13 shows an enlarged bottom view of the tool shown in FIG. 12.

FIG. 14 shows another section view of the tool.

FIGS. 15-22 show various source and detector opening arrangements of thetool.

FIG. 23 shows a top view of a tool having a specific implementation ofindicator markings.

FIG. 24 shows a top view of a tool having another specificimplementation of indicator markings.

FIG. 25 shows perspective views of six alternative implementations of atool.

FIG. 26 shows bottom views of the six alternative implementations.

FIGS. 27A-27G show a fourth alternative implementation of the tool inuse.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an oximeter system 101 for measuring oxygen saturation oftissue in a patient. The system includes a system unit 105 and a sensorprobe 108, which is connected to the system unit via a wired connection112. Connection 112 may be an electrical, optical, or another wiredconnection including any number of wires (e.g., one, two, three, four,five, six, or more wires or optical fibers), or any combination of theseor other types of connections. In other implementations of theinvention, however, connection 112 may be wireless such as via a radiofrequency (RF) or infrared communication.

Typically, the system is used by placing the sensor probe in contact orclose proximity to tissue (e.g., skin or nerve) at a site where anoxygen saturation or other related measurement is desired. The systemunit causes an input signal to be emitted by the sensor probe into thetissue (e.g., human tissue). There may be multiple input signals, andthese signals may have varying or different wavelengths. The inputsignal is transmitted into or through the tissue.

Then, after transmission through or reflection off the tissue, thesignal is received at the sensor probe. This received signal is receivedand analyzed by the system unit. Based on the received signal, thesystem unit determines the oxygen saturation of the tissue and displaysa value on a display of the system unit.

In an implementation, the system is a tissue oximeter, which can measureoxygen saturation without requiring a pulse or heart beat. A tissueoximeter of the invention is applicable to many areas of medicine andsurgery including plastic surgery and spinal surgery. The tissueoximeter can make oxygen saturation measurements of tissue where thereis no pulse; such tissue, for example, may have been separated from thebody (e.g., a flap) and will be transplanted to another place in thebody.

Aspects of the invention are also applicable to a pulse oximeter. Incontrast to a tissue oximeter, a pulse oximeter requires a pulse inorder to function. A pulse oximeter typically measures the absorbancesof light due to the pulsing arterial blood.

There are various implementations of systems and techniques formeasuring oxygen saturation such as discussed in U.S. Pat. Nos.6,516,209, 6,587,703, 6,597,931, 6,735,458, 6,801,648, and 7,247,142.These patents are assigned to the same assignee as this patentapplication and are incorporated by reference.

FIG. 2 shows greater detail of a specific implementation of the systemof FIG. 1. The system includes a processor 204, display 207, speaker209, signal emitter 231, signal detector 233, volatile memory 212,nonvolatile memory 215, human interface device or HID 219, I/O interface222, and network interface 226. These components are housed within asystem unit enclosure. Different implementations of the system mayinclude any number of the components described, in any combination orconfiguration, and may also include other components not shown.

The components are linked together using a bus 203, which represents thesystem bus architecture of the system. Although this figure shows onebus that connects to each component, the busing is illustrative of anyinterconnection scheme serving to link the subsystems. For example,speaker 209 could be connected to the other subsystems through a port orhave an internal direct connection to processor 204.

A sensor probe 246 of the system includes a probe 238 and connector 236.The probe is connected to the connector using wires 242 and 244. Theconnector removably connects the probe and its wires to the signalemitter and signal detectors in the system unit. There is one cable orset of cables 242 to connect to the signal emitter, and one cable or setof cables 244 to connect to the signal detector. In an implementationthe cables are fiber optic cables, but in other implementations, thecables are electrical wires.

Signal emitter 231 is a light source that emits light at one or morespecific wavelengths. In a specific implementation, two wavelengths oflight (e.g., 690 nanometers and 830 nanometers) are used. In otherimplementations, other wavelengths of light may be used. The signalemitter is typically implemented using a laser diode or light emittingdiode (LED). Signal detector 233 is typically a photodetector capable ofdetecting the light at the wavelengths produced by the signal emitter.

The connector may have a locking feature; e.g., insert connector, andthen twist or screw to lock. If so, the connector is more securely heldto the system unit and it will need to be unlocked before it can beremoved. This will help prevent accidental removal of the probe.

The connector may also have a first keying feature, so that theconnector can only be inserted into a connector receptacle of the systemunit in one or more specific orientations. This will ensure that properconnections are made.

The connector may also have a second keying feature that provides anindication to the system unit which type of probe is attached. Thesystem unit may handle making measurements for a number of differenttypes of probes. When a probe is inserted, the system uses the secondkeying feature to determine which type of probe is connected to thesystem. Then the system can perform the appropriate functions, use theproper algorithms, or otherwise make adjustments in its operation forthe specific probe type.

For example, when the system detects a cerebral probe is connected, thesystem uses cerebral probe algorithms and operation. When the systemdetects a thenar probe is connected, the system uses thenar probealgorithms and operation. A system can handle any number of differenttypes of probes. There may be different probes for measuring differentparts of the body, or different sizes or versions of a probe formeasuring a part of the body (e.g., three different thenar probemodels).

With the second keying feature, the system will be able to distinguishbetween the different probes. The second keying feature can use any typeof coding system to represent each probe including binary coding. Forexample, for a probe, there are four second keying inputs, each of whichcan be a logic 0 or 1. With four second keying inputs, the system willbe able to distinguish between sixteen different probes.

Typically, probe 246 is a handheld tool and a user moves the probe fromone point to another to make measurements. However, in someapplications, probe 246 is part of an endoscopic instrument or roboticinstrument, or both. For example, the probe is moved or operated using aguiding interface, which may or may not include haptic technology.

In various implementations, the system is powered using a wall outlet orbattery powered, or both. Block 251 shows a power block of the systemhaving both AC and battery power options. In an implementation, thesystem includes an AC-DC converter 253. The converter takes AC powerfrom a wall socket, converts AC power to DC power, and the DC output isconnected to the components of the system needing power (indicated by anarrow 254). In an implementation, the system is battery operated. The DCoutput of a battery 256 is connected to the components of the systemneeding power (indicated by an arrow 257). The battery is rechargedusing a recharger circuit 259, which received DC power from an AC-DCconverter. The AC-DC converter and recharger circuit may be combinedinto a single circuit.

The nonvolatile memory may include mass disk drives, floppy disks,magnetic disks, optical disks, magneto-optical disks, fixed disks, harddisks, CD-ROMs, recordable CDs, DVDs, recordable DVDs (e.g., DVD-R,DVD+R, DVD-RW, DVD+RW, HD-DVD, or Blu-ray Disc), flash and othernonvolatile solid-state storage (e.g., USB flash drive),battery-backed-up volatile memory, tape storage, reader, and othersimilar media, and combinations of these.

The processor may include multiple processors or a multicore processor,which may permit parallel processing of information. Further, the systemmay also be part of a distributed environment. In a distributedenvironment, individual systems are connected to a network and areavailable to lend resources to another system in the network as needed.For example, a single system unit may be used to collect results fromnumerous sensor probes at different locations.

Aspects of the invention may include software executable code orfirmware (e.g., code stored in a read only memory or ROM chip). Thesoftware executable code or firmware may embody algorithms used inmaking oxygen saturation measurements of the tissue. The softwareexecutable code or firmware may include code to implement a userinterface by which a user uses the system, displays results on thedisplay, and selects or specifies parameters that affect the operationof the system.

Further, a computer-implemented or computer-executable version of theinvention may be embodied using, stored on, or associated with acomputer-readable medium. A computer-readable medium may include anymedium that participates in providing instructions to one or moreprocessors for execution. Such a medium may take many forms including,but not limited to, nonvolatile, volatile, and transmission media.Nonvolatile media includes, for example, flash memory, or optical ormagnetic disks. Volatile media includes static or dynamic memory, suchas cache memory or RAM. Transmission media includes coaxial cables,copper wire, fiber optic lines, and wires arranged in a bus.Transmission media can also take the form of electromagnetic, radiofrequency, acoustic, or light waves, such as those generated duringradio wave and infrared data communications.

For example, a binary, machine-executable version, of the software ofthe present invention may be stored or reside in RAM or cache memory, oron a mass storage device. Source code of the software of the presentinvention may also be stored or reside on a mass storage device (e.g.,hard disk, magnetic disk, tape, or CD-ROM). As a further example, codeof the invention may be transmitted via wires, radio waves, or through anetwork such as the Internet. Firmware may be stored in a ROM of thesystem.

Computer software products may be written in any of various suitableprogramming languages, such as C, C++, C#, Pascal, Fortran, Perl, Matlab(from MathWorks, www.mathworks.com), SAS, SPSS, JavaScript, AJAX, andJava. The computer software product may be an independent applicationwith data input and data display modules. Alternatively, the computersoftware products may be classes that may be instantiated as distributedobjects. The computer software products may also be component softwaresuch as Java Beans (from Sun Microsystems) or Enterprise Java Beans (EJBfrom Sun Microsystems).

An operating system for the system may be one of the Microsoft Windows®family of operating systems (e.g., Windows 95, 98, Me, Windows NT,Windows 2000, Windows XP, Windows XP x64 Edition, Windows Vista, WindowsCE, Windows Mobile), Linux, HP-UX, UNIX, Sun OS, Solaris, Mac OS X,Alpha OS, AIX, IRIX32, or IRIX64. Microsoft Windows is a trademark ofMicrosoft Corporation. Other operating systems may be used, includingcustom and proprietary operating systems.

Furthermore, the system may be connected to a network and may interfaceto other systems using this network. The network may be an intranet,internet, or the Internet, among others. The network may be a wirednetwork (e.g., using copper), telephone network, packet network, anoptical network (e.g., using optical fiber), or a wireless network, orany combination of these. For example, data and other information may bepassed between the computer and components (or steps) of a system of theinvention using a wireless network using a protocol such as Wi-Fi (IEEEstandards 802.11, 802.11a, 802.11b, 802.11e, 802.11g, 802.11i, and802.11n, just to name a few examples). For example, signals from asystem may be transferred, at least in part, wirelessly to components orother systems or computers.

In an embodiment, through a Web browser or other interface executing ona computer workstation system or other device (e.g., laptop computer,smartphone, or personal digital assistant), a user accesses a system ofthe invention through a network such as the Internet. The user will beable to see the data being gathered by the machine. Access may bethrough the World Wide Web (WWW). The Web browser is used to downloadWeb pages or other content in various formats including HTML, XML, text,PDF, and postscript, and may be used to upload information to otherparts of the system. The Web browser may use uniform resourceidentifiers (URLs) to identify resources on the Web and hypertexttransfer protocol (HTTP) in transferring files on the Web.

FIG. 3A shows a block diagram of an implementation of the inventionwhich can facilitate accurate measurements of oxygen saturation oftissue by ensuring that the sensor head is being properly held againstthe tissue. A probe or tool 305 is used by a user 310 to makemeasurements, such as oxygen saturation measurements, of a patient (ortissue) 315. The tool may be referred to as a sensor unit holder. Atypical user is a physician, surgeon, doctor, nurse, technician, orother health care professional. The patient is typically a human patientwho is undergoing a surgical procedure such as a free tissue or freeflap transfer reconstruction. However, the tool may be used innonsurgical procedures. The tool may be used with nonhuman patients suchas animals (e.g., pigs, dogs, cats, horses, cows, rabbits, rats, andmonkeys).

The tool includes a handle 320 so that the tool can be held, a sensorhead or unit 325, and a pressure control mechanism 330 between thehandle and the sensor head. The pressure control mechanism helps toensure that the user does not press the sensor head too tightly againstthe tissue via the handle. The pressure control mechanism can helpensure that a proper pressure or force or a range of proper pressures orforces of the sensor head against the tissue is maintained asmeasurements are made.

In some cases, it can be difficult to attach the sensor unit to thetissue to be monitored such as by using an adhesive pad or tape. Fluidssuch as blood around the surgical site or intraoperative sterile fieldcan reduce the adhesion of the pad. The sensor may then slip or fall offthe tissue. However, simply holding the sensor unit against the tissuemay result in inaccurate measurements because the user may not be ableto hold the sensor unit in a steady position against the tissue.Variations in pressure of the sensor head against the tissue such aspressing the sensor head too tightly or too lightly against the tissuecan result in incorrect measurements. For example, too much pressure onthe tissue can disturb the local perfusion and alter the measurements(e.g., alter the tissue's actual oxygen saturation). This pressurecontrol mechanism can help reduce the pressure variation.

In a specific implementation, the sensor head is part of an oximetersystem for measuring oxygen saturation of tissue in a patient such asthe system shown in FIGS. 1-2 and discussed above. In this specificimplementation, the sensor head includes an arrangement of sourcestructures which transmit radiation or light into the tissue and anarrangement of detector structures which receive the transmitted lightor a portion of the transmitted light so that oxygen saturationmeasurements can be determined. Some examples of source and detectorstructure arrangements are shown in FIGS. 15-22. This tool can be usedduring reconstructive microsurgical procedures where there is a need tobe able to measure one or more regions of a flap intraoperatively, i.e.,during the surgery.

One of skill in the art will recognize that any sensor head may usedwith this tool to make any measurement where it is desirable to ensurethat the sensor head is not pressed too tightly against the tissue. Someexamples of other measurements that may be made with other types ofsensor heads include temperature, blood pressure, chemicalconcentration, or flow measurements, or any other physiologicalmeasurements.

In a specific implementation, the pressure control mechanism is amechanical arrangement or design. The mechanical arrangement may includea spring (i.e., an elastic body or device that recovers its originalshape when released after being distorted). In this specificimplementation, the pressure control mechanism is passive and does notinclude electrical components (e.g., electrical wiring and straingauges) to help the user maintain the proper pressure (or a range ofproper pressures) of the sensor head against the tissue.

The absence of electrical components in the pressure control mechanismallows the tool to be manufactured economically or at a lower cost ascompared to other tools which may include electrical components to sensepressure or force. In this specific implementation, the tool is designedto be disposable, such as after one use. In another implementation, thepressure control mechanism instead or additionally includes electricalcomponents. For example, an electrically operated pressure sensor may beplaced on the sensor head to detect the pressure being applied to thetissue by the sensor head. A pressure sensor may be positioned betweenthe tissue and the sensor head. A pressure sensor may be positionedbetween the tissue and a base of the tool. Components of the pressurecontrol mechanism may include electrical wiring, strain gauges,semiconductor strain gauges, piezoresistors, or combinations of these.

In a specific implementation, the tool including the sensor head orsensor unit, cable or wires, and connector are packaged as a probe unitin a package that is sterile. The probe unit is detachable from theconsole after use and may be disposed. The user can then open a newpackage containing a new probe unit. The package may be opened at thetime of actual use or near the time of actual use so as to notcontaminate the probe unit. The user can then connect this new probeunit that is sterile to the console to begin monitoring. This disposablefeature helps to ensure a sterile field around the patient.

FIG. 3B shows a schematic diagram of a specific implementation of a tool350. The tool includes a handle 351 connected to a first spring 353connected to an offset 356 connected to a base 359 connected to a sensorhead 362. Second springs 365 (such as a resilient foam pad), inparallel, are connected to the base and at least partially surround orentirely surround the sensor head. A cable 368 runs from the sensorhead, along the base, offset, and first spring and into and through thehandle where the cable connects to a system unit such as the system unitshown in FIG. 1. The tool further includes a stop pin 371 and a limitregion 373 having a pair of limit stops, i.e., upper limit stop 376 andlower limit stop 379.

In brief, a sequence of operation for the tool is:

1. A user holds the handle and positions the sensor head or sensor unitto face a tissue to be measured.

2. The user applies a force or moment to the handle against a bias forceof the spring and in a direction towards the tissue so that the sensorunit is held against the tissue.

3. As the user applies the force the spring flexes as the handle moves,rotates, pivots, or travels towards the tissue and the sensor headexerts a force or pressure on the tissue as result of the applied forceat the handle. The user can gauge or estimate the pressure being appliedto the tissue by observing the position of the stop pin relative to thepair of limit stops. For example, in a specific implementation, the toolis designed or calibrated so that the upper limit stop indicates that adesired maximum pressure to apply to the tissue via the tool has beenexceeded.

Thus, the user can observe the distance between the upper limit stop andthe stop pin. So long as the user maintains a gap between the upperlimit stop and the stop pin, the user will know that an excess level ofpressure or force is not being applied to the tissue.

In a specific implementation, the cable includes one or more opticalfibers or optical fiber bundles. The optical fibers transmit light fromthe system console to sensor openings (i.e., source sensor openings) onthe sensor head or base and into the tissue. Light from the tissue isreceived by sensor openings (i.e., detector sensor openings) on thesensor head or base and is transmitted back to the system console. Endsof the optical fiber are connected to the sensor openings and oppositeends of the optical fiber are connected to light sources or detectors(e.g., photodiodes) at the system console. In this specificimplementation, the cable does not include electrical wires.

In other implementations, the cable includes electrical wires. The cablemay include electrical wires and optical fiber. The cable may includeelectrical wires and no optical fiber. For example, in a specificimplementation, a light source such as a light emitting diode is at thesensor unit. The cable may then include an electrical wire to supplypower to the light emitting diode. As another example, a detector suchas a photodiode or photodetector is at the sensor unit. The cable maythen include an electrical wire to transmit an electrical signalproduced by the photodiode back to the system console.

The offset may be designed to be a rigid member relative to the springs.The offset allows the handle to be positioned away from the base. Inother words, in this specific implementation, the handle is not directlyabove the base. Rather, the handle is off to a side of the base or isoffset (i.e., laterally offset) in a horizontal direction from aposition vertically above the base. The handle is positioned in adirection upwardly and obliquely from the base.

In an implementation, a line coincident with a direction of gravitypasses through the base (i.e., passes through the sensor unit or passesthrough a sensor opening or sensor structure of the sensor unit). Asecond line extends in a direction perpendicular to the first line untilthe second line intersects a surface of the handle. The first line doesnot pass through the handle. A distance between the first line and thehandle may be represented by the offset. The amount of offset may be thelength of the second line. The offset amount can range from about 1millimeter to about 100 millimeters. This includes, for example, 10, 15,20, 25, 30, 35, 40, 50, 60, 70, 80, 90, or 99.9 millimeters. The amountcan be greater than 100 millimeters or less than 1 millimeter.

In another implementation, an outline encircling the sensor openingsdefines a boundary line. A boundary region bounded by the boundary lineextends in a vertical direction or in a direction perpendicular to aplane in which the sensor openings lie. In this specific implementation,the handle is offset from the sensor openings such that the handle doesnot intersect the boundary region.

The absence of a handle or other structure above the base or sensor uniteliminates or minimizes interference by the handle thus permitting thesensor unit to, for example, slide between two tissues to makemeasurements.

Further, the specific amount of offset can be used individually or incombination with other design variables to determine the pressure orforce at the tissue in response to an applied force or moment at thehandle. For example, the offset may be considered as a moment or leverarm. The first spring can be a linear spring or a torsional spring. Theforce of a spring, such as a linear spring, is given by:F=−kx  (1)

where x is the displacement of the end of the spring and k is the springconstant. Similarly, the torque of a torsional or rotational spring is:t=−kθ  (2)

where θ is the angle of twist of the spring from its equilibriumposition in radians and k is the spring constant (i.e., torsioncoefficient, torsion elastic modulus, or rate). These equations may bereferred to as Hooke's Law or Hooke's Law of Elasticity. Hooke's Law isan approximation that states the extension of a spring is in directproportion with the load added to it as long as this load does notexceed the elastic limit. Above a certain stress or force which may bereferred to as the elastic limit or yield strength of an elasticmaterial, the solid (e.g., the spring) may deform irreversibly,exhibiting plasticity. Generally, the forces discussed in thisapplication applied to the spring to bend the spring will be within theelastic range (not plastic range) of the spring. In otherimplementations, the forces will exceed the elastic range of the spring.

The torque or moment of a force with respect to a point is:m=Fd  (3)

where F is the force applied at a distance d from the point. In animplementation, distance d is a length of the offset or lever arm.

As one of skill in the art will recognize, variables such as the springconstant, length of the lever arm, distance between the upper and lowerlimits, number of springs, arrangement of springs (e.g., springs inparallel and springs in series), and combinations of these can be variedto produce a desired pressure at the sensor unit in response to anapplied force or moment at the handle. The tool can be designed so thatthe pressure or force at the tissue will be less than, equal to, orgreater than the force applied at the handle.

Factors that may contribute to the spring constant include the springdimensions such as the spring's length, width, or thickness, shape orcross-sectional shape of the spring which can affect a moment ofinertia, the material that the spring is made of (e.g. plastic ormetal), or combinations of these.

An implementation may include two or more springs in series (e.g.,springs linked end-to-end), two or more springs in parallel (e.g.springs side-by-side), or a combination of springs in series and springsin parallel. For springs in parallel, the equivalent spring constant ofthe combination is a sum of the spring constants of each individualspring. For springs in series, to find the equivalent spring constant ofthe combination, add the reciprocals of the spring constants of eachindividual spring and take the reciprocal of the sum.

First spring 353 may be on either or both sides of the offset. In thisspecific implementation, first spring 353 is on a first side (e.g.,right-hand side) of the offset. The offset is between the base and thefirst spring. In another implementation, the first spring is on a secondside (e.g., left-hand side) of the offset, opposite the first side. Thefirst spring is between the base and the offset. In anotherimplementation, there is a spring on the first side of the offset andanother spring on the second side of the offset.

In other implementations, the handle is not offset from the base. Thatis, the handle is above or directly above the base. An example of suchan implementation is alternative design four shown in FIGS. 25-27G.

FIG. 4 shows a side view of a specific implementation of a tool 405. Thetool includes a handle 408, a base 411, and a pressure control mechanism414 between the handle and the base. A sensor unit 417 and a pad or foampad 420 at least partially surrounding the sensor unit are attached to abottom surface of the base. A cable 423 is connected to the sensor unitand is routed through the tool. The handle includes a set of ridges 424which alternate with a set of valleys 425.

The pressure control mechanism includes a gauge 427 and a spring 435.The gauge includes a stop or stop pin 429 and a recess or limit region438 that has a pair of limit stops—an upper limit stop 447 and a lowerlimit stop 463. The stop pin is engaged or received between the upperand lower limit stops.

The spring is connected between the base and the handle so that there isa first gap 441 formed between the handle and an extension 432. A secondgap 444 is formed between upper limit stop 447 at a top end of therecess and the stop pin. The second gap may be referred to as a pressurelimiting gap. The stop pin engages the recess or is received between theupper and lower limit stops.

In this specific implementation, when the user applies a force or momentto the handle, the handle rotates or pivots downward about the springand towards the tissue, closing the first and second gaps. That is, theupper limit stop moves towards the stop pin. The user can gauge thepressure being applied to the tissue by the tool by observing thedistance or size of the second gap between the upper limit stop and thestop pin. The tool is calibrated or designed so that as long as there isa gap (i.e., second gap) a force being applied to the tissue by the toolis below a threshold or excessive level.

In a specific implementation, the travel of the handle is stopped (i.e.,limited) when upper limit stop contacts or touches the stop pin. Inanother implementation, the travel of the handle is stopped when thehandle contacts or touches a top surface of the extension below thehandle. This top surface may be referred to as a travel limitingfeature. In a specific implementation, the upper limit stop contacts thestop pin and a bottom surface of the handle contacts the top surface ofthe extension when a predetermined force is applied to the handle by theuser. The predetermined force may range from about 57 grams (i.e., 2ounces) to about 85 grams (i.e., 3 ounces).

The pressure control mechanism can provide a visual indication of thedesirable levels or range of pressures or forces being applied to thetissue via the tool. Specifically, it can be difficult for the user tomaintain a steady or constant pressure of the sensor unit or face of thesensor unit against the tissue. For example, the user's hand may lackthe dexterity, the user's muscles may be tense, the user's hand may growtired or become fatigued as the surgery progresses, the user may benervous, and so forth. This can lead to tremors or “shaky” hands whichcan adversely affect the measurements. Applying excessive force candisturb the local perfusion, and therefore alter the tissue's actualoxygen saturation. Applying too little force can allow ambient light toslip between the pad and the tissue which can reduce signal quality.

This pressure control mechanism can help to ensure a constant pressureof the sensor unit against the tissue despite the variation in pressureapplied to the tool or handle by the user. The pressure controlmechanism may compensate for variation in pressure applied by the user.The pressure control mechanism can absorb excess levels of force to helpensure that the forces are not transmitted to the tissue beingmonitored. The pressure control mechanism can help ensure that adesirable pressure or force or range of desirable pressures or forces isapplied against the tissue.

In this specific implementation, the handle is offset from the base viathe extension. Typically, the extension is relatively stiff or rigid ascompared to the spring. The spring is connected at a first end 459 ofthe handle. A bottom surface of the handle extending from the first endto a second end 462 of the handle, opposite the first end, extendswithout projecting over any sensor opening of the sensor unit. Thesecond end of the handle is nearer the sensor unit than the first end ofthe handle. In this specific implementation, there are no structuressuch as the handle above a region of a top surface of the base where thesensor unit is directly below the region.

Since there are no structures, such as the handle, above the base orsensor unit this results in a very low-profile design. This designallows the sensor unit to be positioned or slide into tight or confinedareas where space is limited. A stud 426 to which the stop pin isconnected may act as a stop or horizontal stop to indicate a depthwithin the tissue that the sensor unit can be inserted. In otherimplementations, the handle is directly above the base. For example,FIGS. 25-26 show a tool 4 having a handle directly above the base. FIGS.27A-G show tool 4 in use.

In a specific implementation, a thickness or height of the base asmeasured from a tissue facing surface of the sensor unit to the topsurface of the base is about 6 millimeters or less than 6 millimeters.The thickness can range from about 3 millimeters to about 12millimeters. This includes, for example, 4, 5, 7, 8, 9, 10, 11, or 11.9millimeters, or more than 12 millimeters. The thickness may be less than3 millimeters.

In a specific implementation, a thickness of the pad in an uncompressedstate is about 3 millimeters, but can range from about 1 millimeter toabout 6 millimeters. This includes, for example, 1.5, 2, 2.5, 3.5, 4,4.5, 5, 5.5, 5.9 millimeters, or more than 6 millimeters. The thicknessmay be less than 1 millimeter. A thickness of the sensor head or unitmay be equal to or greater than the thickness of the pad in theuncompressed state. A thickness of the sensor head may be less than thethickness of the pad in the uncompressed state.

In a specific implementation, a thickness of the base measured withoutthe pad is about 2 millimeters, but can range from about 0.5 millimetersto about 5 millimeters. This includes, for example, 1, 1.5, 1.6, 1.7,1.8, 1.9, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3,3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.5, 4.9 millimeters, or more than 5millimeters. The thickness may be less than 0.5 millimeters.

The region of the top surface of the base over the sensor unit openingsmay have a surface area that is equal to or greater than a surface areaof the sensor unit. A distance from a distal edge 452 of the base to thestud may be about 27 millimeters, but can range from about 15millimeters to about 40 millimeters. This includes, for example, 17, 19,21, 22, 23, 24, 25, 26, 28, 29, 30, 31, 32, 33, 34, 35, 37, 39, 39.9millimeters, or more than 40 millimeters. The distance may be less than15 millimeters.

The extension includes a first end 453 and a second end 456, oppositethe first end. The first end is connected to an end of the base or issupported by the base. The second end is unsupported by the base. Thatis, the extension is cantilevered relative to the base (i.e., having oneend supported and an opposite end unsupported). The extension may bereferred to as a platform.

Similarly, the handle includes first end 459 and a second end 462opposite the first end. The second end of the handle is unsupported. Thefirst end of the handle is supported via the spring. The spring isconnected between the first end of the handle and the second end of theextension. The handle is cantilevered or is suspended over theextension, creating the first gap.

As shown in FIG. 4, this specific implementation of the gauge includesstud 426 which projects from a top surface of the base, opposite thebottom surface of the base. At an end of the stud is the stop pin whichprojects into or is received by the recess or limit region or travellimit region of the handle. The stop pin is fixed relative to the baseand the recess is fixed relative to the handle. The handle is positionedbetween the stud and the spring.

In this specific implementation, the limit region is positioned at thefirst end of the handle. The limit region includes the pair of limitstops to limit a travel of the handle relative to the sensor unit. Thereis lower limit stop 463 at a bottom end of the limit region and upperlimit stop 447 at a top end of the limit region, opposite the bottomend. The stop pin is between the upper and lower limit stops of thelimit region. In this specific implementation, the limit region is arecess formed above the first gap and on a surface of the handle nearestthe sensor unit. The recess is formed along a portion of a spine 465 ofthe handle which divides the tool into first and second halves orportions. The recess may be formed anywhere on the handle so long as thestop pin is able to project into the recess. The recess may be referredto as a notch, indentation, depression, or groove.

Note that the mechanical arrangement of the pressure control mechanismshown in FIG. 4 is merely an example of one particular implementation.In other implementations, other similar and equivalent elements andfunctions may be used or substituted in place of what is shown. Forexample, the recess or limit region is shown on the handle (or fixedrelative to the handle) and the stop pin is shown on the base (or fixedrelative to the base). However, these components can be swapped. Therecess may be fixed relative to the base and the stop pin may be fixedrelative to the handle.

As another example, the spring is shown near one end of the handle andthe gauge (i.e., the stop pin and limit region) are shown near anotheropposite end of the handle. In the arrangement shown, a first distancebetween the sensor unit and spring is greater than a second distancebetween the sensor unit and the stop pin, limit region, or both. Forexample, the limit region or pair of limit stops is closer to the sensorunit than the spring.

However, the position of the spring can be swapped with the position ofthe stop pin and limit region so that the spring is closer to the sensorunit than the stop pin and the limit region. For example, spring iscloser to the sensor unit than the limit region or pair of limit stops.

Although in this example the limit region has been implemented as arecess, the recess may be replaced with a pair of protrusions or bumpersextending from a surface of the handle. These protrusions can act asupper and lower limit stops for the stop pin to bump against.

A distance between the upper and lower limit stops is proportional to adistance that the handle can travel towards the sensor unit. Thus,spreading the upper and lower limit stops further apart allows thehandle to travel further. The gauge may include markings or referencemarkings on the limit region that when aligned with the stop pinindicates the degree or distance that the handle has traveled. Themarkings may be color coded. For example, the upper limit stop or aregion near the upper limit stop may be colored red to indicate that thedesired maximum pressure has been reached or exceeded.

FIG. 5 shows a perspective view of tool 405 with the sensor unitomitted. The view is looking from a proximal end of the tool towards adistal end of the tool.

FIG. 6 shows a side view of tool 405. A dimension H5 indicates a heightof the tool, a dimension L5 indicates a length of the tool. Sectionviews 7-7, 9-9, and 14-14 are shown in FIGS. 7, 9, and 14, respectively.

In a specific implementation, spring 435 is designed to flex or bendwhen the user applies a force of about 42 grams (i.e., 1.5 ounces) tothe handle. However, this force or threshold force can range from about20 grams to about 200 grams. The force can range from about 0 grams (orounces) to about 142 grams (i.e., 5 ounces). The force can range fromabout 57 grams (i.e., 2 ounces) to about 85 grams (i.e., 3 ounces). Forexample, the force can be about 15, 25, 30, 40, 45, 50, 55, 60, 65, 70,80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, or 199 grams,or more than 200 grams. In an implementation, second gap 444 is closed(i.e., upper limit stop 447 and stop pin touch) when a force rangingfrom about 57 grams (i.e., 2 ounces) to about 85 grams (i.e., 3 ounces)is applied to the handle.

This wide-range of forces to close the second gap can address thedifferent degrees of dexterity that different users may have. Forexample, some users may have very steady nerves. For these users, aspring having a lower stiffness may be desirable. Other users may haveless dexterity and less sensitivity. For these other users, a springhaving a higher stiffness may be desirable.

In a specific implementation, a desired user applied force to the handleis represented by a range of forces including a desired minimum forceand a desired maximum force. The spring may be designed so that thedesired user applied force is equal to or greater than the forcerequired to initially deflect the spring from a first or precompressedcondition to a second or further compressed condition. In theprecompressed condition, a distance between lower limit stop 463 andstop pin 429 is less than a distance between upper limit stop 447 andthe stop pin. For example, the distance may be zero where the lowerlimit stop and stop pin touch or contact.

In this specific implementation, the desired maximum force is that forcejust below the force required to compress the spring such that upperlimit stop 447 contacts stop pin 429. The desired maximum force may bethe force required to compress the spring such that the upper limit stopcontacts the stop pin.

In this specific implementation, the user can feel the spring deflectionor handle move when applying force to the handle. The user can see thetravel of the handle as the spring deflects by observing the increasingdistance between the lower limit stop and the stop pin as the userapplies force to the handle or by observing the decreasing distancebetween the upper limit stop and the stop pin. As the lower limit stopis observed moving away from the stop pin, the user is given anindication that the desired minimum force has been reached or exceeded.As the upper limit stop approaches the stop pin, the user is given anindication that the maximum desired force is approaching. When the upperlimit stop contacts the stop pin, the user is given an indication thatthe maximum desired force has been reached or exceeded.

Thus, the distance between the upper and lower limit stops can indicatethe range of desired user applied forces. Within this range, the sensorunit is able to make accurate measurements. When the minimum force hasbeen reached, there will be sufficient contact between the sensor unitor bottom surface of the base and the tissue. Specifically, for example,there will be no or little interference from ambient light; light fromthe source structures of the sensor unit will be able to properly passinto the tissue; and light from the tissue will be properly detected bythe detector structures of the sensor unit.

In an implementation, the spring's flexibility is similar to that ofhard rubber or soft plastic. The spring may have a type A durometer thatranges from about 70 to about 100. Typically, stiffness is the amount offorce required to cause a unit of deformation or displacement and may bereferred to as a spring constant.

In this specific implementation, the spring is made of plastic.Specifically, polypropylene homopolymer pro-fax 6523.

The spring is molded together or integrally as a single unit or unitarybody with some of the other components of the tool such as the handle,base, stop pin, and extension. These components may all be formed fromthe same material. Making these components from the same material andsame mold can help to reduce manufacturing costs.

Any process may be used to make the tool (e.g., injection molding). Acolorant such as titanium dioxide bright white colorant may be added tomake the tool white. One benefit of a white or light-colored tool isthat it can provide a contrasting background for stains such as blood onthe tool. This can indicate that caution should be taken when using thetool as the tool may have become contaminated with blood. For example,the blood may be blocking one or more of the sensor openings on thebottom surface of the base which may result in erroneous readings.

In another implementation, two or more of the components such as thespring and the handle are made separately such as by using separatemolds. The components may then be connected together using any techniquesuch as gluing or welding (e.g., plastic welding).

Generally, the spring can be made of any flexible, medical gradebiocompatible plastic material. Some examples include medical gradepolypropylene, polyethylene, and polyurethane. In other implementations,the spring is made of metal (e.g., steel, stainless steel, titanium, orcopper). The spring and handle may be made of different materials. Forexample, the spring may be made of steel and the handle may be made ofplastic.

Although FIG. 6 shows the spring positioned at an end of the first gapor handle, the spring may be positioned anywhere so long as it allowsthe handle to move, travel, pivot, or flex in response to pressureapplied by the user. For example, the spring may be positioned betweenone end of the gap and an opposite end of the first gap. A spring may bepositioned between the stop pin and the cable.

Further, although the figures show one spring, it should be appreciatedthat there can be more than one spring, such as two, three, or more thanthree springs. Each spring may have the same spring constant, stiffness,or force constant. Two or more springs may have different springconstants. There can be first and second springs connected between thehandle and the base or sensor unit. A stiffness of the first spring maybe the same or different from a stiffness of the second spring.

Other factors affecting spring stiffness may include the spring shape,dimensions, or both. For example, FIG. 7 shows section view 7-7 fromFIG. 6. The section view is a top view which shows a cross section ofspring 435 at second end 456 of extension 432. Circle 8 refers to adetailed view of the second end of the extension which is shown in FIG.8. Extension 432 includes an opening 705. The extension is connected viaa ramp 710 to base 411. The ramp is at an incline relative to the baseand is at a decline relative to the extension. In other words, from theextension to the base the ramp slopes down; from the base to theextension the ramp slopes up.

Referring now to FIG. 8, the spring at its middle has a first thicknessT10 and at its opposite ends a second thickness T15. A line 805 parallelto an x-axis 810 a passes through a center (or reference point) 807 ofthe spring. Line 805 divides the tool longitudinally. A line 810parallel to a y-axis 810 b which projects out of the page passes throughcenter 807 and is perpendicular to line 805. A line 815 parallel to az-axis 810 c passes through center 807 and is perpendicular to lines 805and 810.

When a force is applied to the handle, the spring flexes or bends aboutline 815 and the handle rotates or pivots about line 815. The stiffnessof the spring and thus the amount of force used to bend the spring isproportional to the thickness of the spring. Thus, increasing the firstthickness, second thickness, or both can increase the amount of forceused to bend the spring. Conversely, decreasing the first thickness,second thickness, or both can decrease the amount of force used to bendthe spring.

In a specific implementation, first thickness T10 is about 1.3millimeters (i.e., 0.05 inches), but can range from about 0.5millimeters to about 5 millimeters. This includes, for example, 0.6,0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2,2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 4, or 4.9 millimeters, or morethan 5 millimeters. The first thickness may be less than 0.5millimeters.

The thickness of the spring tapers from a middle portion of the springand outwards towards the opposite ends of the spring. In other words, inthis specific implementation, there is a gradual diminution of thicknessas one moves from the middle portion of the spring and outwards towardsthe ends of the spring. Thus, second thickness T15 is less than firstthickness T10. In a specific implementation, second thickness T15 isabout 0.8 millimeters (i.e., 0.03 inches), but can range from about 0.1millimeters to about 3 millimeters. This includes, for example, 0.2,0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.4, 1.5, 1.6, 1.7, 1.8,1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, or 2.9 millimeters, ormore than 3 millimeters. The second thickness may be less than 0.1millimeters.

As shown in FIG. 8, in this specific implementation, spring 435 has across-sectional shape of a lozenge or diamond. In other words, thecross-sectional shape has four equal sides and two acute angles and twoobtuse angles. The two acute angles are opposite each other. The twoobtuse angles are opposite each other. The spring is oriented so thatline 805 bisects the two obtuse angles and line 815 bisects the twoacute angles.

This shape and orientation of the spring may be used to facilitate theassembly of the tool. For example, in a specific implementation, whenthe tool is removed from the mold the tool is in an unassembled state.In the unassembled state, the sensor unit, cable, and pad are not yetattached. The handle may be oriented such that the limit region orrecess on the handle and the stop pin are not yet engaged. To assemblethe tool, the manufacturer can grasp the base and handle, twist thehandle about line 810 so that the bottom end of the recess can slipbelow the stop pin (see FIG. 4), push the handle down towards the basethus bending the spring about line 815, and then release the handle toallow the spring to untwist so that the bottom end of the recess slipsbelow the stop pin. Having the thickness at the opposite ends of thespring being less than the thickness in the middle of the spring canfacilitate the twisting of the spring about line 810 during assembly.

Although FIG. 8 shows the spring having a diamond-shaped cross section,a spring can have any cross-sectional shape such as a rectangle, square,triangle, circle, oval, ellipse, and so forth.

In a specific implementation, the spring is formed as a c-shaped springor a flat strip spring. However, any type of spring may be used. Someexamples of spring types include tension or extension springs,compression springs, torsion springs, coil or helical springs, conicalsprings, balance springs, and leaf springs (i.e., laminated or carriagespring). The spring may be referred to as a flexible strip or resistingmember (e.g., force-resisting member).

In a specific implementation, the spring is implemented as a livinghinge. Such a hinge may be a thin flexible hinge made from plastic thatjoins two rigid plastic parts together (e.g., base and handle), allowingthem to bend along the line of the hinge. The living hinge may bemanufactured in an injection molding operation that creates all threeparts at one time as a single part. The living hinge may be made from aresin such as polyethylene or polypropylene.

Referring now to FIG. 6, the handle includes an upper set of valleys 610and ridges 615, a lower set of valleys 620 and ridges 625, a firstchannel 630 between the upper and lower sets of valleys and ridges, anda set of openings 635 along the first channel. There is a second channel640 below extension 432. The handle further includes an upper spine 645and a lower spine 650.

One or more components of the tool such as the handle may be designed tobe not or minimally reflective. This can help ensure that more of thelight which is transmitted into the tissue is received back at thedetectors, instead of being reflected off the tool. For example, asurface of the tool may be coated with an antireflective material (suchas a black oxide coating) to make it less reflective than the originalstarting material. One or more surface portions of the tool may becolored (e.g., black flat color), or finished (e.g., matte finish), ortextured (e.g., bead-blasted finish) to reduce reflectivity. Anotherbenefit of reducing reflectivity is that there will be less glare forthe surgeon and other medical people during the operation.

One or more components of the tool may be made of a transparent,semi-transparent, or opaque material. In a specific implementation, thecord or portions of the cord within the handle are visible (FIG. 4). Thecord or portions of the cord are exposed via openings 635 (FIG. 6). Thecord or portions of the cord may instead or additionally be exposedthrough a transparent or semi-transparent material.

In a specific implementation, openings 635 include a first set ofopenings on a first side of the handle and a second set of openings on asecond side of the handle, opposite the first side. In this specificimplementation, the first and second sets of openings are offset or areshifted from each other. That is, an opening of the first set ofopenings is not aligned with an opening of the second set of openings. Afirst opening of the first set of openings overlaps a portion of asecond opening of the second set of openings and a portion of a thirdopening of the second set of openings. Offsetting the openings can makethe handle stronger as compared to a handle where the openings are notoffset or are aligned. Offsetting the openings can make the handle moreresistant to bending as compared to a handle where the openings arealigned. In another implementation, the first and second sets ofopenings are aligned with each other.

An opening may be bounded by two opposite walls of the first channel anda pair of struts extending between the two opposite walls of the firstchannel. A strut on one side of the handle may be offset from a strut onan opposite side of the handle. For example, in a specificimplementation, (as shown in FIGS. 5 and 6) on a first side 515 of thehandle (FIG. 5) there is a first reference point 520 on a first wall 525of the first channel and a second reference point 526 on a second wall530 of the first channel. A first strut 535 extends between the firstand second reference points. On a second side 670 of the handle (FIG. 6)there is a third reference point 672 on the first wall of the firstchannel and a fourth reference 673 point on the second wall of the firstchannel. The third and fourth reference points are directly opposite thefirst and second reference points. In this specific implementation, asecond strut 674 does not extend between the third and fourth referencepoints. Rather, on the second side of the handle there is a fifthreference point 678 above fourth reference point 673 and a sixthreference point 680 above third reference point 672. The second strutextends between fifth reference point 678 and sixth reference point 680.

The upper and lower spines extend perpendicularly outward from thechannel and generally curve arcuately away from the base and towards aproximal end of the handle. A height of a portion of the upper spine asmeasured from the first channel may progressively decrease as one movestowards the proximal end of the handle.

The upper spine bisects the upper set of valleys and ridges. In aspecific implementation, the upper spine includes a first slope 652 anda second slope 653 which meet at a transition point 654. The secondslope is between the first slope and the limit region or recess. Thesecond slope is steeper than the first slope.

The lower spine bisects the lower set of valleys and ridges. A height ofthe upper spine may be different from a height of the lower spine. Inthis specific implementation, the height of the upper spine is greaterthan the height of the lower spine. In other implementations, the heightof the upper spine is less than the height of the lower spine. Theheights of the upper and lower spines are the same. The spines can helpmake the handle rigid.

In this specific implementation, the ridges and valleys are alternating.There is a ridge which is followed by an adjacent valley. A thickness ofthe ridge may be the same as a thickness of the adjacent valley. Athickness of a first ridge or valley is the same as a thickness of asecond ridge or valley. In another implementation, the thickness of theridge is different from the thickness of the adjacent valley ornonadjacent valley. Two or more ridges may have different thicknesses.Two or more valleys may have different thicknesses.

The valleys and ridges and openings 635 can help improve the user's gripon the handle so that the tool does not accidentally slip from theuser's hand. For example, fluids such as blood are typically presentduring surgical procedures. The blood may be mixed with fat cells orother debris and tissue which can coat the various surgical tools makingthe tools slippery. The valleys can help draw the blood away from thesurface of the handle by providing a place for the blood to collect sothat the handle does not become slippery with fluids.

The valley and ridge feature and openings 635 also helps to reduce theweight of the handle as compared to a solid handle and can make the tooleasier to hold. This can be desirable during long surgical procedureswhere the user must hold the tool for an extended period of time. Thesefeatures can also facilitate the manufacture of the handle by making thetool easier to mold. Further, because of these features less material isrequired to make the handle which lowers manufacturing costs.

A surface 655 of the handle may include ergonomic features such astextures, knurls (i.e., a series of small ridges or beads), or both toaid in gripping. In this specific implementation, the handle is designedto be gripped or pinched on its opposite sides between the user's thumband middle finger while the forefinger or index finger rests on a frontsurface 660 (or a portion of the front surface).

In this specific implementation, the front surface is above limit region438 and is between a first side of the handle and a second side of thehandle, opposite the first side. The front surface may be planar or flatto provide a comfortable resting place for the user's forefinger. Inanother implementation, the front surface is curved such as curvedconcave to provide a depression in which the user's forefinger can rest.The front surface may be curved convex.

FIG. 9 shows section view 9-9 from FIG. 6. A dimension W5 indicates awidth of the front surface. In a specific implementation, W5 is about14.5 millimeters (i.e., 0.57 inches), but can range from about 10millimeters to about 20 millimeters. This includes, for example, 11, 12,13.1, 13.2, 13.3, 13.4, 13.5, 13.6, 13.7, 13.8, 13.9, 14, 14.1, 14.2,14.3, 14.4, 14.6, 14.7, 14.8, 14.9, 15, 15.1, 15.2, 15.3, 15.4, 15.5,15.6, 15.7, 15.8, 15.9, 16, 17, 18, 19, 19.9 millimeters, or more than20 millimeters. Width W5 may be less than 10 millimeters.

FIGS. 10 and 11 show rear and top views, respectively of the handle. Asshown in FIGS. 10 and 11, the handle's width or a portion of thehandle's width may taper. For example, as shown in FIG. 10, the width ofthe bottom portion of the handle may be constant. Thereafter, as shownin FIG. 11, the width of the top portion of the handle may vary. Adimension W10 indicates a first width of the bottom portion of thehandle (FIG. 10). A dimension W15 indicates a second width of the topportion of the handle (FIG. 11). The top portion of the handle tapersfrom the first width to the second width. The tapering of the handle canmake the handle comfortable to hold.

In a specific implementation, width W10 is about 18.5 millimeters (i.e.,0.73 inches), but can range from about 10 millimeters to about 25millimeters. This includes, for example, 11, 12, 13, 14, 15, 16, 16.5,17, 17.5, 18, 19, 19.5, 20, 21, 22, 23, 24, or 24.9 millimeters, or morethan 25 millimeters. Width W10 may be less than 10 millimeters. WidthW15 is about 14.2 millimeters (i.e., 0.56 inches), but can range fromabout 7 millimeters to about 20 millimeters. This includes, for example,8, 9, 10, 11, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 18,19, or 19.9 millimeters, or more than 20 millimeters. Width W15 may beless than 7 millimeters.

The size of the tool such as its height H5 (FIG. 6), length L5 (FIG. 6),and width of the base W20 (FIG. 13) may vary greatly depending upon theapplication, the user's preference, or both. In a specificimplementation, height H5 is about 50.1 millimeters (i.e., 2.05 inches),but can range from about 30 millimeters to about 75 millimeters. Thisincludes, for example, 35, 40, 45, 50, 55, 60, 65, 70, or 74.9millimeters, or more than 75 millimeters. Height H5 may be less than 30millimeters.

Length L5 is about 82.6 millimeters (i.e., 3.25 inches), but can rangefrom about 50 millimeters to about 150 millimeters. This includes, forexample, 60, 70, 80, 90, 100, 110, 120, 130, 140, or 149 millimeters, ormore than 150 millimeters. Length L5 may be less than 50 millimeters.

Width W20 is about 21.3 millimeters (i.e., 0.84 inches), but can rangefrom about 10 millimeters to about 50 millimeters. This includes, forexample, 15, 20, 25, 30, 35, 40, 45, or 49 millimeters, or more than 50millimeters. Width W20 may be less than 10 millimeters.

FIG. 12 shows a bottom view of tool 405. Circle 13 refers to a detailedview shown in FIG. 13. Base 411 includes a bottom surface 1305. Aportion of second channel 640 extends onto the bottom surface of thebase. An outline 1310 indicates the position of the sensor unit attachedto the bottom surface of the base.

Second channel 640 includes a first wall 1315 and a second wall 1320,opposite the first wall. The first and second walls extendperpendicularly away from the bottom surface of the base. The wallsbegin at a proximal edge of the outline of the sensor unit, extend pastthe bottom surface of the base, and terminate at the spring (see FIG.6). A tab 1325 extends from one of the walls in a direction parallel tothe bottom surface and towards the other wall.

The second channel and tab help to secure and guide the sensor unitcable. For example, when the tool is assembled the sensor unit cable isrouted through the second channel and slipped below the tab. In thisspecific implementation, the tab terminates before reaching the otherwall. This provides a space between the tab and the other wall so thatthe cable can be placed in the space and slipped beneath the tab. Thecable is placed so that it is between the first and second channelwalls.

In this specific implementation, the second channel is positionedequidistant from two opposite edges of the base. In otherimplementations, the channel is placed offset from a centerline passinglongitudinally through the base. For example, the distance between thefirst wall of the channel and a first edge of the base may be differentfrom a distance between the second wall of the channel and a second edgeof the base, opposite the first edge of the base.

In a specific implementation, a distance D5 from one wall to a nearestedge or edge of the base is about 6.8 millimeters (i.e., 0.27 inches),but can vary greatly. A distance D10 indicates a distance between thefirst and second walls. See also FIG. 14. In a specific implementation,distance D10 is about 6.8 millimeters (i.e., 0.27 inches), but can varygreatly. Distance D10, D5, or both may vary proportionally with a widthof the cable. A distance D15 indicates a distance from an edge of theoutline for the sensor unit to a side edge of the base. In a specificimplementation, distance D15 is about 6.1 millimeters (i.e., 0.24inches), but can vary greatly.

The routing of the sensor unit cable is shown in FIG. 4. The cablepasses through the first channel and along a portion of the extension,into opening 750 of the extension (FIG. 7), across the first gap, intothe first channel, and then exits the proximal end of the handle. Thisrouting can help to improve cable strain resistance. It should beappreciated that the cable may be routed different from what is shown inFIG. 4. For example, the cable may be routed so that it is on top of thesurface of the handle instead of being routed through the channel.

FIG. 15 shows a specific implementation of a sensor unit. Such a sensorunit may be incorporated in the various probe implementations (e.g.,tool 305 or 405) discussed above in this application.

This sensor has six openings 1501-1506. Openings 1501-1504 are arrangedin a line closer to a first edge of the sensor, while openings 1505 and1506 are arranged closer to a second edge, which is opposite the firstedge. In fact, opening 1506 is closer than opening 1505 to the secondedge. These openings are for sources and detectors, and there can be anynumber of sources, any number of detectors, and they can be in anycombination. In an implementation of a sensor head, the first edge isdistal to the second edge, which is closer to a cable attached to theprobe or hand holding the probe.

In one implementation, openings 1501-1504 are detectors while openings1505 and 1506 are sources. However, in other implementations, there canbe one or more detectors, two or more detectors, one or more sources, ortwo or more sources. For example, there may be three detectors and threesources or one detector and five sources.

In FIG. 15, the openings are positioned asymmetrically such that a linedrawn through openings 1501-1504 is not parallel to a line drawn throughopenings 1505 and 1506. However, a line drawn through openings 1501 and1505 is parallel to a line through openings 1504 and 1506. Additionally,the distance between openings 1501 and 1504 is shorter than the distancebetween openings 1505 and 1506.

Thus, the distance between openings 1501 and 1505 does not equal thedistance between openings 1501 and 1506; the distance between openings1502 and 1505 does not equal the distance between openings 1503 and1505; and the distance between openings 1503 and 1505 does not equal thedistance between openings 1504 and 1506.

In this implementation, the sensor unit has a rectangular shape, but thesensor unit may have any shape such a trapezoid, triangle, dodecagon,octagon, hexagon, square, circle, or ellipse. A sensor of any shape orform can incorporate the sensor openings in the pattern shown anddescribed.

In a specific implementation, a distance between openings 1501 and 1504is five millimeters. A distance between each of the openings 1501, 1502,1503, and 1504 is 5/3 millimeters. A distance between 1501 and 1505 isfive millimeters. A diameter of an opening is one millimeter.

FIG. 16 shows a variation of the implementation of the sensor unit shownin FIG. 15. The sensor unit in this specific implementation is alsoarranged to include six openings 1601-1606. Similar to FIG. 15, openings1601-1604 are arranged in a line closer to a first edge of the sensor,while openings 1605 and 1606 are arranged closer to a second edge, whichis opposite the first edge. In one implementation, openings 1601-1604are detectors while openings 1605 and 1606 are sources.

In this figure, the openings are positioned so that a line drawn throughopenings 1601-1604 is parallel to a line through openings 1605 and 1606.However, a line drawn through openings 1601 and 1605 is not parallel toa line through openings 1604 and 1606.

Additionally, similar to FIG. 15, the distance between openings 1601 and1604 is shorter than the distance between openings 1605 and 1606. Thus,the distance between openings 1601 and 1605 does not equal the distancebetween openings 1601 and 1606; the distance between openings 1602 and1605 does not equal the distance between openings 1603 and 1605; and thedistance between openings 1603 and 1605 does not equal the distancebetween openings 1604 and 1606.

In this implementation, the sensor unit itself is of a greater arearelative to the area of the sensor unit shown in FIG. 15. In anotherimplementation, the sensor unit may be of a smaller area relative to thearea shown in FIG. 15. In yet another implementation, the sensor unitmay be of a greater area relative to that shown in FIG. 16.

Further, in a specific implementation, the openings are the same size aseach other (e.g., each opening has the same diameter or each opening hasthe same area). A specific implementation uses one-millimeter circularopenings. However, in another implementation, the diameter of oneopening may be different from other openings, or there may be someopenings with different diameters than other openings. There can be anycombination of differently sized openings on one sensor unit. Forexample, there are two openings with a C size and other openings have aD size, where C and D are different and D is greater than C. Also,openings are not necessarily circular. So, C and D may represent areavalues.

FIG. 17 shows another variation of the implementation of the sensor unitshown in FIG. 15. The sensor unit in this specific implementation isalso arranged to include six openings 1701-1706. Similar to FIGS. 15 and16, openings 1701-1704 are arranged in a line closer to a first edge ofthe sensor, while openings 1705 and 1706 are arranged closer to a secondedge, which is opposite to the first edge. In one implementation,openings 1701-1704 are detectors while openings 1705 and 1706 aresources.

In this figure, the openings are positioned so that a line drawn throughopenings 1701-1704 is parallel to a line through openings 1705 and 1706.In fact, these two lines are equal in length. Furthermore, a line drawnthrough openings 1701 and 1705 is parallel (and equal in length) to aline through openings 1704 and 1706.

Thus, in this specific implementation, the distance between openings1701 and 1706 is equal to the distance between openings 1704 and 1705.This specific arrangement includes further equalities: the distancebetween openings 1702 and 1705 equals that between openings 1703 and1706 and the distance between openings 1703 and 1705 equals that betweenopenings 1702 and 1706.

In an implementation, the distances between openings 1701-1704,1704-1706, 1706-1705, and 1705-1701 are all equal; thus, in thisimplementation openings 1701, 1704, 1706, and 1705 form the vertices ofa square. In other implementations, however, four openings may form thevertices of any quadrilateral, such as a rectangle, a rhombus, atrapezoid, or a parallelogram.

Aside from the equalities mentioned, the distances between each of theopenings 1701-1704 and each of the openings 1705-1706 are not equal. Forinstance, the distance between openings 1701 and 1705 does not equal thedistance between openings 1701 and 1706.

FIG. 18 shows a specific implementation of a sensor unit which isarranged to include four openings 1801-1804. Openings 1801 and 1802 arearranged in a line closer to a first edge of the sensor, while openings1803 and 1804 are arranged closer to a second edge, which is oppositethe first edge. In fact, opening 1804 is closer than opening 1803 to thesecond edge. In an implementation the first edge is distal to the secondedge, which is closer to a cable attached to the probe or hand holdingthe probe.

In one implementation, openings 1801 and 1802 are detectors and openings1803 and 1804 are sources. However, in other implementations, there canbe one or more detectors, two or more detectors, one or more sources, ortwo or more sources. For example, there may be three detectors and onesource or one detector and three sources.

In FIG. 18, the openings are positioned asymmetrically such that a linedrawn through openings 1801 and 1802 is not parallel to a line throughopenings 1803 and 1804. However, a line drawn through openings 1801 and1803 is parallel to a line through openings 1802 and 1804.

Additionally, the distance between openings 1801 and 1802 is shorterthan the distance between openings 1803 and 1804. Thus, in FIG. 18, thedistance between openings 1801 and 1803 does not equal the distancebetween openings 1802 and 1804 and the distance between openings 1802and 1803 does not equal that between openings 1802 and 1804.

FIG. 19 shows a variation of the implementation of the sensor unit shownin FIG. 18. The sensor unit of this implementation also includes fouropenings 1901-1904. Openings 1901 and 1902 are arranged in a line closerto a first edge of the sensor, while openings 1903 and 1904 are arrangedcloser to a second edge, which is opposite the first edge. In oneimplementation, openings 1901 and 1902 are detectors and openings 1903and 1904 are sources.

In FIG. 19, the openings are positioned symmetrically such that a linedrawn through openings 1901 and 1902 is parallel, and equal, to a linethrough openings 1903 and 1904. Additionally, a line drawn throughopenings 1901 and 1903 is parallel, and equal, to a line throughopenings 1902 and 1904.

In an implementation, the distances between openings 1901-1902,1902-1904, 1904-1903, and 1903-1901 are all equal; thus, in thisimplementation openings 1901, 1902, 1903, and 1904 form the vertices ofa square. In other implementations, however, four openings may form thevertices of any quadrilateral, such as a rectangle, a rhombus, atrapezoid, or a parallelogram.

Some of the distances between the centers of particular openings areunequal; for instance, the distance between openings 1901 and 1903 doesnot equal the distance between openings 1901 and 1904.

FIG. 20 shows another variation of the implementation of the sensor unitshown in FIG. 18. Similar to FIGS. 18 and 19, this specificimplementation of a sensor unit includes four openings 2001-2004.

However, in this variation, all four of the openings are arranged in aline closer to a first edge of the sensor. Specifically, in this figure,openings 2001-2004 lie in a row parallel to the first edge so that astraight line may be drawn through each opening. In one implementation,openings 2001 and 2002 are detectors and openings 2003 and 2004 aresources.

In this specific implementation, the distance between openings 2001 and2002 is equal to the distance between openings 2002 and 2003; thisdistance is also equal to that between openings 2003 and 2004.

Additionally, the distance between openings 2001 and 2003 equals thatbetween openings 2002 and 2004. In fact, this distance is twice thedistance between each individual opening. Thus, the distance betweenopenings 2001 and 2003 does not equal that between openings 2001 and2002; the former is twice the distance of the latter.

FIG. 21 shows a variation of the implementation of the sensor unit shownin FIG. 20. This implementation of a sensor unit is similarly arrangedto include four openings 2101-2104. Also, this arrangement of openingsis located closer to a first edge of the sensor. However, in thisfigure, openings 2101, 2102, and 2104 lie in a row parallel to the firstedge so that a straight line may be drawn through the center of eachopening, while opening 2103 lies below that straight line.

In this implementation, opening 2103 lies equally spaced betweenopenings 2102 and 2104; in other implementations, opening 2103 can liecloser to one opening than another. In one implementation, openings 2101and 2102 are detectors and openings 2103 and 2104 are sources.

In this specific implementation, as mentioned above, the distancebetween openings 2102 and 2103 equals that between openings 2103 and2104. Aside from this equality, the distances between the openings areunequal. For example, in this implementation, the distance betweenopenings 2101 and 2103 does not equal the distance between openings 2102and 2104 and the distance between openings 2102 and 2103 does not equalthat between openings 2102 and 2104.

FIG. 22 shows a specific implementation of a sensor unit which isarranged to include two openings 2201 and 2202. Similar to FIGS. 20 and21, this arrangement of openings is located closer to a first edge ofthe sensor. Additionally, openings 2201 and 2202 lie in a row parallelto the first edge so that a straight line may be drawn through eachopening. In one implementation, opening 2201 is a detector and opening2202 is a source.

Although we have shown sensor units with two, four, and six openings inthese figures, other implementations may include different numbers ofsensor openings. For instance, there may be three, five, seven, eight,or more than eight openings.

Although the openings are shown as circles, an opening can have anyshape, including obround, oblong, oval, ellipse, square, rectangle,triangle, or other shapes. A sensor unit can include openings havingdifferent shapes such as an opening having one shape (e.g., circle) andanother opening having a different shape (e.g., square).

There may be any combination of detectors and sources and the number ofdetectors need not equal the number of sources. For instance, if thereare three openings, there may be one detector and two sources or twodetectors and one source. As another example, if there are eightopenings, there may be two detectors and six sources, five detectors andthree sources, or four detectors and four sources.

Further, one or more sensor openings may be covered with a film such asa light-transparent film, a semitranslucent film, or a light diffusingfilm. Such a film can help attenuate the light back-reflected from thetissue. The sensor openings may be covered with a protective cover,sleeve, or barrier. In this specific implementation, light from thesensor openings can pass through the protective cover and into thetissue. Light from the tissue can pass through the protective cover andbe detected by the detector structures. The protective cover can beremoved and a new protective cover can be placed on the tool for a nextuse or next patient.

In a specific implementation, a sensor arrangement includes a firstsource structure, a second source structure, a first detector structurethat includes optical fiber, and a second detector structure. A firstdistance extends between the first source structure and the firstdetector structure without touching another source or detectorstructure. A second distance extends between the second source structureand the second detector structure without touching another source ordetector structure. A third distance extends between the second sourcestructure and the first detector structure without touching anothersource or detector structure. A fourth distance extends between thefirst source structure and the second detector structure withouttouching another source or detector structure. The first distance isdifferent from the second and third distances. The second distance isdifferent from the third distance.

In various implementations, the fourth distance is different from thefirst, second, and third distances. There are no source or detectorstructures between the first and second source structures. There are nosource or detector structures between the first source structure and thefirst detector structure. The first source structure and first detectorstructure have the same cross-sectional area. A fifth distance betweenthe first and second source structures is greater than a sixth distancebetween the first and second detector structures.

In implementations discussed so far in this application, each opening onthe bottom surface of the base or sensor unit has a single fiberassociated with it. However, in further implementations of theinvention, each opening may have multiple fibers-two or more-associatedwith it. Or, each opening of the probe may have multiple light paths orlight channels associated with it.

These light paths can be used simultaneously for transmitting to tissueor receiving light from tissue. Within a single opening, there may betwo source structures, two detector structures, or one source and onedetector structure. And for a single tool, probe, or sensor unit of thetool, there may be two or more such openings with multiple lightchannels.

The bottom surface of the base may include one opening having aconcentric core fiber with an inner core light channel which issurrounded by an outer core light channel. In a specific implementation,the inner core light channel is a source channel and the outer corelight channel is a detector channel. However, in another implementation,the inner core light channel is a detector channel and the outer corelight channel is a source channel. Furthermore, in anotherimplementation, the inner and outer core light channels may not beconcentric. For example, the inner and outer core light channels may notshare the same centers. Openings having two or more fibers are furtherdiscussed in U.S. patent application Ser. No. 12/194,508, filed Aug. 19,2008, which is incorporated by reference.

Source and detector arrangements are further discussed in U.S. Pat. No.7,355,688, issued Apr. 8, 2008; U.S. Pat. No. 7,525,647, issued Apr. 28,2009; and U.S. Pat. No. 7,538,865, issued May 26, 2009; and U.S. patentapplication Ser. No. 12/126,860, filed May 24, 2008; Ser. No.12/194,508, filed Aug. 19, 2008; and Ser. No. 12/359,792, filed Jan. 26,2009 which are incorporated by reference along with all other referencescited in this application.

In a specific implementation, the sensor openings for the source anddetector arrangements are part of a sensor unit. The sensor unit is aseparate part or component. In another implementation, the sensoropenings are formed directly on the base itself or a portion of thebase. Optical wires (e.g., fiber optic cables) may be routed through thetool and directly connected to the individual sensor openings on thebase itself. A beam combiner may be included in the console as discussedin U.S. Pat. No. 7,355,688.

FIG. 23 shows a top view of a specific implementation of a tool 2305. Atop surface 2310 of the base includes a set of markings, indicators, orvisual indicators 2315. The set of markings includes first, second, andthird arrows 2320 a-c, and first and second brackets 2325 a-b.

First arrow 2320 a points towards a left-hand side edge 2330 of thebase. Second arrow 2320 b points towards a right-hand side edge 2335 ofthe base, opposite the left-hand side edge. Third arrow 2320 c pointstowards a top edge 2340 of the base which joins the left and right-handside edges.

The arrows can be located or positioned anywhere along the edges of thebase. In a specific implementation, the first and second arrows arelocated at about a midpoint between the top edge of the base and a stoppin 2345. A distance from the top edge of the base to the first arrow isequal to a distance from the stop pin to the first arrow. Similarly, adistance from the top edge of the base to the second arrow is equal to adistance from the stop pin to the first arrow. The third arrow islocated at a midpoint of the top edge or between the left and right-handside edges. A distance from the left-hand side edge to the third arrowis equal to a distance from the right-hand side edge to the third arrow.

The brackets or square brackets can be located anywhere on the topsurface of the base. In this specific implementation, the brackets arelocated below or behind the third arrow. The second bracket is a mirrorimage of the first bracket. The brackets are located at a midpointbetween first and second arrows.

The brackets indicate a position of the sensor unit attached to thebottom surface of the base with respect to the top surface of the base.The brackets indicate an outline or at least a portion of the outline ofthe sensor unit. The first bracket indicates a top portion of an outlineof the sensor unit. The second bracket indicates a bottom portion of theoutline of the sensor unit.

The arrows serve as a reference point so that the tool can be removedfrom a location on the tissue and then later repositioned at that samelocation and orientation. This allows repeatable readings ormeasurements to be made. For example, the user can position the toolover the tissue to be measured. Using a surgical marking pen, the usercan make marks or dots on the tissue or skin such that each dot isaligned with one of the first, second, or third arrows. The tool canthen be removed and later repositioned at the same location by aligningor matching the dots and the arrows. In a specific implementation, ifone were to draw a cross through the dots (e.g., the three dotscorresponding to the three arrows), the intersection would indicate thecenter of the sensor unit.

In an implementation, a method for using the tool includes placing thesensor unit over a tissue to be measured. The sensor unit is placed onthe tissue such that it is over a specific location on the tissue and isin a specific orientation with respect to the tissue. The methodincludes making at least one dot (e.g., mark) on skin adjacent, near, ornext to the tissue to be measured. The at least one dot corresponds toor is aligned with at least one visual indicator on the tool. The skinmay surround, border, or at least partially surround or border thetissue to be measured. The tool can then be removed from the tissue andrepositioned over the specific location on the tissue and in thespecific orientation. This can be done by positioning the tool on thetissue such that the at least one dot on the skin is aligned with the atleast one visual indicator on the tool.

In another implementation, the at least one dot may be made on thetissue to be measured (e.g., on skin above the tissue to be measured).For example, the tool may include a hole passing from the top surface ofthe base to the bottom surface of the base. In this specificimplementation, the user can mark the skin above the tissue to bemeasured by passing a tip of a surgical pen through the hole and markingthe skin. The tool can be repositioned by aligning the mark on the skinwith the hole.

The arrows, brackets, or both can help in assisting or aiding the user(e.g., surgeon) to determine the active region of the sensor unit sothat the sensor unit can be aligned over the tissue or region ofinterest to be measured.

The markings may be made using any technique for making a visibleimpression on the tool including, but not limited to, printing,silkscreen printing, masking, stamping, plating, thermography,embossing, painting, engraving, etching, anodizing, oxidizing,deposition, imprinting, and chemical processing. The marking may be madeanywhere on the tool such as the top surface of the base as shown in thefigure, a side surface of the base which joins the top and bottomsurfaces of the base, or both. The marking may be a bump or notch thatis perceptible by touch. However, it is generally desirable that themarking is visible while looking down towards the top surface of thetool.

FIG. 24 shows a top view of a base of a tool 2405 having indicatorarrows and no brackets. There are first, second, and third arrows 2410a-c, respectively. The first arrow points towards a first side edge ofthe base. The second arrow points towards a second side edge of thebase, opposite the first side edge. The third arrow points towards a topedge of the base, between the first and second side edges. That is, thetop edge joins the first and second side edges.

In a specific implementation, a first plane passing through the firstand second arrows divides a bottom surface of the base into first andsecond regions. In this specific implementation, the first region hasdetector structures and no source structures. The second region hassource structures and no detector structures. The second region iscloser to the handle than the first region. In another implementation,the first region is closer to the handle than the second region.

In another implementation, a second plane passes through the third arrowand intersects or is perpendicular to the first plane. The second planedivides the bottom surface of the base into third and fourth regions. Inthis specific implementation, the third region has at least one detectorstructure and at least one source structure. The fourth region has atleast one detector structure and at least one source structure. A numberof detector structures in the third region may be equal to or differentfrom a number of detector structures in the fourth region. A number ofsource structures in the third region may be equal to or different froma number of source structures in the fourth region. A region can havedetector structures and no source structures. A region can have sourcestructures and no detector structures. A number of detector structuresin a region may be less than, equal to, or greater than a number ofsource structures in the region.

In this specific implementation, a distance from the top edge of thebase to the first and second arrows is about a quarter of the length ofthe base from the top edge to the bottom edge of the base.

In some implementations, there are no markings. There can be arrowindicators and no bracket indicators such as shown in FIG. 24. There canbe bracket indicators and no arrow indicators. Further, the bracket andarrow indicators are merely some specific examples of visual indicators.Other examples or types of visual indicators, graphics, or symbolsincluding letters, characters, numbers, words, lines, pictures, images,icons, shapes (e.g., triangles), and so forth.

FIGS. 25-26 show top and bottom views, respectively, of six alternativedesigns for the tool. In alternative designs 1-2 and 5-6, the handledoes not project over the base. In alternative design 1, the tool isformed as a c-shape. The handle is formed as a hook. The handle extendsover the extension and there is a gap below the handle or between thehandle and the extension. In alternative design 2, the handle is formedas a hoop, loop, or circle. The extension is the spring which connectsthe base and the handle. In this specific implementation, the spring istangent to the handle. In alternative design 5, the handle is formed asan elongated member with a textured surface. The handle is connected tothe base via an extension which acts as a spring. A distal end of thehandle includes a stop, indicator, or protrusion which contacts thespring to limit a travel of the handle. In alternative design 6, thehandle has a smooth surface.

In alternative design 3, a handle includes a pair of ring sections.There is a pad having a cavity to hold a sensor unit, a base connectedto the pad and positioned over the cavity, a first ring sectionextending from a surface of the plate, and a second ring section. Thesecond ring section is a mirror image of the first ring section. Thefirst and second ring sections define an opening to receive a user'sfinger. When the opening receives the finger a portion of the finger isabove the sensor unit. In this specific implementation, ends of thefirst and second ring sections do not touch. In another implementation,the ends of the first and second ring sections touch to define a closedcircle or ring.

In alternative design 4, there is a bottom base layer having an opening,a top base layer, a handle connected to the top base layer, and a padhaving a cavity. The pad is connected between the bottom and top baselayers. The opening overlaps at least a portion of the cavity. The padis more compliant than the bottom and top base layers. Applying athreshold level of force to the handle causes at least a portion of thepad to be compressed between the bottom and top base layers. A surfaceof the handle is textured. The texturing includes a set of concentriccircles or groves around the handle which extend from one end of thehandle to an opposite end of the handle. The handle is formed as anelongated bulb-shaped part which makes the handle comfortable to hold.In this specific implementation, the cable is not routed through thehandle.

FIGS. 27A-G show alternative design 4 and a method of using the tool. Ina specific implementation, the tool includes a pair of gambrels or postsextending through a pair of openings in the top base layer. An area ofan opening in the pair of openings is greater than a cross-sectionalarea of a gambrel. Thus, a portion of the pad is visible from the topbase layer through the pair of openings.

In this specific implementation, the tool may be used by pushing thehandle forwards, sideways, or diagonally to ensure sufficient contactbetween the bottom base layer and the tissue. As the handle is pushed orpulled, the top base layer tilts with respect to the bottom base layeras portions of the pad are compressed. In other words, the bottom baselayer remains in sufficient contact with the tissue as the handle ispushed or pulled such that light does not escape from the cavity (oronly a small amount of light escapes) and ambient light does not enterthe cavity (or only a small amount of ambient light enters).

A position of the pair of gambrels relative to the pair of openings canprovide an indication of the pressure being applied to the tissue. Forexample, the position of a gambrel within an opening may indicateexcessive pressure is being applied to the tissue such as when thegambrel touches or contacts an edge of the opening. The position of thegambrel within an opening may indicate an uneven pressure is beingapplied to the tissue such as when one gambrel within one opening is ata position different from another gambrel within another opening.

Referring now to FIG. 6, a representative flow for making tool 405 isdescribed in steps 1 to 5 below.

1. Provide the tool, the tool being in an unassembled state.

2. Assemble the pressure control mechanism of the tool.

3. Route the sensor unit cable through the tool.

4. Attach the sensor unit that is at a first end of the cable to thebottom surface of the base.

5. Attach the pad to the bottom surface of the base.

6. Attach a connector to a second end of the cable, opposite the firstend.

Although the steps above are listed in a specific order, the steps maytake place in any order, as desired and depending on the specificapplication. There may be additional or other steps, which may replaceone or more of the above steps. Certain steps may be repeated. Certainsteps may be omitted. For example, step 2 may be omitted where a moldfor the tool allows the tool to be produced such that the pressurecontrol mechanism is assembled (i.e., the stop pin is aligned within therecess of the handle).

In step 1 of the flow, the tool is provided in an unassembled state. Thetool may be provided using any type of manufacturing process such asinjection molding. In injection molding, a material (e.g. plasticgranules) is forced into a mold cavity where it cools and hardens to theconfiguration of the mold cavity. The tool is then removed from thecavity. Colorants may be added during the molding process.

In a specific implementation, the mold includes first, second, and thirdcavities. The first cavity is connected to the second cavity and thesecond cavity is connected to the third cavity. The first cavity is forproducing the tool base or base portion. The second cavity is forproducing the spring portion. The third cavity is for producing thehandle portion. Material such as plastic is injected into the mold whereit cools and hardens to the configuration of the mold cavities. When thematerial or product is removed from the mold, there is then a singlepiece of material or product that includes the base, spring, and handleportions.

In step 2, the pressure control mechanism is assembled. This step mayinclude substeps a-b below.

a. Twist the spring by twisting the handle relative to the base and pushthe two pieces together.

b. Release one of the handle or the base allowing the spring to untwistwith another one of the handle or the base such that the stop pin isaligned within the recess of the handle.

In step 3, the sensor unit cable is routed through the tool. The cableor a portion of the cable may be further secured to the tool via anadhesive such epoxy or glue.

In step 4, the sensor unit which is at a first end of the cable isattached to the bottom surface of the base. The sensor unit may bepositioned on the bottom surface by butting a proximal side edge of thesensor unit against the ends of the channel walls and aligning oppositeside edges of the sensor unit with opposite channel walls, the proximalside edge being between the opposite side edges of the sensor unit. Thesensor unit is attached to the bottom surface of the base such that thesource and detector openings of the sensor unit face away from thebottom surface of the base.

The sensor unit may be secured to the bottom surface of the base via anadhesive such as epoxy which cures into a resin or any other type ofadhesive or glue. Some examples of resins include thermosetting resins,polyester resins, amino resins, polyamide resins, polyvinyl butyralresins, acrylic resins, phenol formaldehyde resins, ketone formaldehyderesins, and alkyd resins.

In step 5, the pad is placed so that it at least partially around thesensor unit. For example, the sensor unit may be bordered on at leastthree sides by pad material. A side of the pad may be coated with anadhesive (e.g., pressure sensitive adhesive) so that the pad may besecured to the bottom surface of the base. The pad may be referred to asa light shield pad. The pad may include a reflective layer or materialthat surrounds or at least partially surrounds the sensor unit. Thereflective layer may be a foil, mirror, or any other material or coatingthat reflects light. The reflective layer can help prevent source lightfrom escaping, reduce ambient light, or both. The pad can help form aseal between the tissue and the tool (i.e., the base portion of thetool).

In a specific implementation, a thickness of the pad in an uncompressedstate is less than a thickness of the sensor unit. A portion of thesensor unit may extend past a surface of the pad. In anotherimplementation, the thickness of the pad in the uncompressed state isthe same as the thickness of the sensor unit. The sensor unit and thesurface of the pad may be coplanar. In another implementation, thethickness of the pad in the uncompressed state is less than thethickness of the sensor unit.

In step 6, attach a connector to a second end of the cable, opposite thefirst end. In a specific implementation, the connector is attached tothe end or second end of the cable after the cable is routed through thetool. If the connector were attached before the cable was routed throughthe tool it might not be possible to route the cable through the toolbecause of the size of the connector. Generally, the cable is routedthrough the tool before attaching the sensor unit, connector, or both toan end of the cable.

An instruction sheet describing how to use the tool may be packaged orincluded with the tool. In a specific implementation, the instructionsinclude a diagram or figure of the tool showing a side view of the tooland a diagram or figure showing a top view of the tool and the referencepoints for location marking. The instructions may further include thefollowing steps:

1. Grasp the handle and gently apply the sensor face to the tissue. Donot allow the handle to bottom out against the base as this means thatexcessive force has been applied.

2. Maintain a pressure-limiting gap as shown (in the figure). Applyingexcessive force will disturb the local perfusion, and therefore alterthe tissue's actual oxygen saturation.

3. To obtain repeatable readings in multiple locations, mark each exactlocation and orientation of the sensor on the skin with a sterilesurgical marking pen using the reference points provided. Pause theconsole while changing locations.

4. Keep sensor and pad dry and free of blood. Do not allow holes onsensor face to become obstructed. The sensor head is surrounded by alight shield pad, however, excessive ambient light may reduce signalquality.

The instruction sheet may further include information that specifies anexpiration date (e.g., a “use by date”), a serial number, size (e.g.,length and width) of the sensor unit, base, or both.

Figures A-U in an appendix of parent U.S. patent application Ser. No.12/623,945 show various implementations for markings on the top surfaceof the base of the tool. Figures V-X show various views of a specificembodiment of the tool. Figures Y-Z show the operation of the pressurelimiting gap for a specific embodiment of the tool. Figure AA shows anexample of an instruction sheet that may be included with the tool.

In a specific implementation, the tool is designed to be disposable,such as after one use. In another implementation, the tool is designedto be reusable. In this specific implementation, a disposabletransparent sleeve or cover may be slipped over at least a portion ofthe base to help protect the base from being contaminated. Afterwards,disposable transparent sleeve may be disposed and the tool itself can bereused by slipping a new disposable transparent sleeve over the base.

As discussed above, in various implementations, measurements are madewhile the user holds the sensor unit via the handle against the tissueto be measured. In specific implementations, the bottom surface of thebase which faces the tissue does not have any adhesives since the sensorunit is being held against the tissue by the user. In other words, aportion of the bottom surface which surrounds or at least partiallysurrounds the sensor openings has no adhesives. There is no releaseliner on the bottom surface.

This description of the invention has been presented for the purposes ofillustration and description. It is not intended to be exhaustive or tolimit the invention to the precise form described, and manymodifications and variations are possible in light of the teachingabove. The embodiments were chosen and described in order to bestexplain the principles of the invention and its practical applications.This description will enable others skilled in the art to best utilizeand practice the invention in various embodiments and with variousmodifications as are suited to a particular use. The scope of theinvention is defined by the following claims.

The invention claimed is:
 1. A method comprising: providing an oximetersystem comprising a handle, electronics, a battery, and a sensor head,wherein the sensor head comprises a probe face that faces a tissue to bemeasured, and the battery is coupled to the electronics; on the probeface, forming first, second, and third sensor structures; positioningthe second sensor structure at a first distance from the first sensorstructure; positioning the third sensor structure at a second distancefrom the first sensor structure, wherein the first distance is differentfrom the second distance, and measurement data received by way of atleast one of the first, second, and third sensor structures is processedby the electronics; and providing an elastic member comprising a springconstant coupled between the sensor head and handle, wherein at least afirst portion of the handle is adapted to be cradled in an area betweena thumb and forefinger of a user's hand.
 2. The method of claim 1wherein the first sensor structure comprises a source structure and thesecond and third sensor structures comprise detector structures.
 3. Themethod of claim 1 wherein the first sensor structure comprises adetector structure and the second and third sensor structures comprisesource structures.
 4. The method of claim 1 wherein the first and secondsensor structures are positioned to form a first line, the first andthird sensor openings are positioned to form a second line, and thefirst line is not parallel to the second line.
 5. The method of claim 1wherein the first, second, and third sensor structures are arranged in aline.
 6. The method of claim 1 comprising: providing a pressure sensoron the sensor head.
 7. The method of claim 1 comprising: coupling alight emitting diode to the first sensor structure; coupling aphotodetector to the second sensor structure; and coupling the batteryto the light emitting diode and the photodetector.
 8. The method ofclaim 1 wherein a first line passes through the sensor head, in a firstdirection that is transverse to the probe face of the sensor head, asecond line extends in the first direction and intersects a surface ofthe handle, the first line passes through the first sensor structure,the first line does not pass through the handle, and a first distance isbetween the first line and the second line in a second direction,transverse to the first direction, wherein the first distance is greaterthan about 1 millimeter.
 9. The method of claim 1 comprising: coupling alight emitting diode to the first sensor structure; coupling aphotodetector to the second sensor structure; and coupling the batteryto the light emitting diode and the photodetector, wherein a first linepasses through the sensor head, in a first direction that is transverseto the probe face of the sensor head, a second line extends in the firstdirection and intersects a surface of the handle, the first line passesthrough the first sensor structure, the first line does not pass throughthe handle, and a first distance is between the first line and thesecond line in a second direction, transverse to the first direction,wherein the first distance is at least about 1 millimeter.
 10. Themethod of claim 1 wherein the oximeter system is a tissue oximeterprobe.
 11. A method comprising: providing an oximeter device comprisinga handle, electronics, a battery, and a probe face, wherein the probeface is to be positioned facing a tissue to be measured, and the batteryis coupled to the electronics; forming at least one sensor structure onthe probe face; providing a pressure sensor at a sensor head, whereinthe sensor head comprises the probe face, and measurement data receivedfrom the pressure sensor is processed by the electronics; and couplingan elastic member comprising a spring constant between the sensor headand the handle, wherein at least a first portion of the handle isadapted to be cradled in an area between a thumb and forefinger of auser's hand.
 12. The method of claim 11 comprising: using the pressuresensor, detecting a pressure being applied to the tissue by the probeface.
 13. The method of claim 11 comprising: coupling the battery to thepressure sensor.
 14. The method of claim 11 comprising: coupling a lightemitting diode to a first sensor structure formed on the probe fac1e ofthe sensor head; and coupling a photodiode to a second sensor structureformed on the probe face.
 15. The method of claim 11 wherein theoximeter device is a tissue oximeter probe.
 16. A method comprising:providing an oximeter system comprising a handle, electronics, abattery, and a probe face, wherein the probe face is to be positionedagainst a tissue to be measured, and the battery is coupled to theelectronics; forming a first sensor structure and a second sensorstructure on the probe face; coupling a light emitting diode to thefirst sensor structure; coupling a photodiode to the second sensorstructure, wherein measurement data received by way of at least one ofthe first sensor structure or the second sensor structure is processedby the electronics; coupling the battery to the light emitting diode andthe photodetector; and coupling a flexible member comprising a springconstant between the probe face and the handle.
 17. The method of claim16 wherein the battery supplies power to the light emitting diode andthe photodetector, and the method comprises: coupling a rechargercircuit to the battery, wherein the recharger circuit recharges thebattery.
 18. The method of claim 16 wherein a first line passes throughthe sensor head, in a first direction that is transverse to the probeface of the sensor head, a second line extends in the first directionand intersects a surface of the handle, the first line passes throughthe first sensor structure, the first line does not pass through thehandle, and a first distance is between the first line and the secondline in a second direction, transverse to the first direction, whereinthe first distance is at least about 1 millimeter.
 19. The method ofclaim 16 comprising: coupling a processing circuit to the light emittingdiode, photodetector, and battery.
 20. The method of claim 16comprising: coupling a processing circuit to the light emitting diode,photodetector, and battery; and a display, coupled to the processingcircuit.
 21. The method of claim 16 wherein the handle comprises: aproximal end; a distal end, closer to the sensor head than the proximalend; a front side, wherein the front side comprises a first portion fromthe proximal end to a first bend having a first slope, and a secondportion from the first bend to the distal end having a second slope; anda back side that is opposite the front side.
 22. The method of claim 21wherein the second slope is steeper than the first slope.
 23. The methodof claim 16 wherein a first line passes through the first sensorstructure and a second line passes through an axis of the handle, andthe first line and second line are angled with respect to each other.24. The method of claim 16 wherein at least a first portion of thehandle is adapted to be cradled in an area between a thumb andforefinger of a user's hand.
 25. The method of claim 24 wherein at leasta second portion of the handle is adapted to be contacted by theforefinger of the user's hand, and the second portion of the handle ison a different side of the handle to the first portion of the handle.26. The method of claim 16 comprising: forming a third sensor structureon the probe face, positioning the second sensor structure at a firstdistance from the first sensor structure; positioning the third sensorstructure at a second distance from the first sensor structure, whereinthe first distance is different from the second distance, wherein atleast a first portion of the handle is adapted to be cradled in an areabetween a thumb and forefinger of a user's hand.
 27. The method of claim16 wherein the oximeter system comprises a tissue oximeter probe. 28.The method of claim 16 wherein the electronics comprises a processor anda memory.